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Community Member

Microsoft NLB multicast on 3750 L3 switch

Hi,

My setup is as follow:

3750 L3--- NLB cluster (multicast mode)

My NLB servers is not able to get arp entry for its default gateway which is on the 3750 L3 switches.

In the arp request by the NLB server, the ethernet header src mac is showing the actual NIC mac address.In the ARP payload, it is showing the source mac as the virtual multicast mac.

Is that normal?

I suppose the 3750 switch do not know how to handle?

Any advise or solution?

6 REPLIES
Silver

Re: Microsoft NLB multicast on 3750 L3 switch

Statically configure an ARP entry pointing the virtual IP to the multicast mac address, and point the multicast mac addresses to the ports in which the servers are connected to.

Community Member

Re: Microsoft NLB multicast on 3750 L3 switch

Hi,

But how and can you configure an arp entry if you have an IP address for 2 mac addresses?

Community Member

Re: Microsoft NLB multicast on 3750 L3 switch

Hi there,

I'm also having a problem on my 3750 with NLB. When I do a sh ip igmp snooping groups, I can see the correct ports in the multicast group. I also have a static arp entry with the virtual IP mapped to the multicast group MAC address. However, I can see that traffic destined for the virtual IP is still being flooded out of all ports. Any ideas where am I going wrong?

Thank you, J

Community Member

Re: Microsoft NLB multicast on 3750 L3 switch

I've been using static MAC address entries (one 0100.5e--.---- address on two ports) to control the flooding, seems to work well.

Dave

Community Member

Re: Microsoft NLB multicast on 3750 L3 switch

I don't use the nlb function, but cluster, the mac address is not the multicast address but the physical mac address of the active server.

and I didn't find any solution about it.

Community Member

Re: Microsoft NLB multicast on 3750 L3 switch

Many thanks Dave, I will give that a try. J

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